RO121460B1 - Method for selectively controlling undesirable vegetation in agricultural crops - Google Patents

Abstract

The invention relates to a method for selectively controlling undesirable vegetation in agricultural crops, by using metal chelates for improving the selectivity of 2-(substituted benzoyl)-1,3 cyclohexanedione compounds as postemergent herbicides in agricultural crops, especially wheat.

Description

The invention relates to a method of selective control of unwanted vegetation in agricultural crops. More specifically, the invention relates to the use of metal chelates in order to improve the selectivity of 2- (benzoyl substituted, 3-cyclohexandionic) compounds as post-emergent herbicides in agricultural crops.

Protecting agricultural crops from weeds and other unwanted vegetation, which inhibits the development of agricultural crops, is a permanent problem in agriculture. To solve this problem, researchers in the field of synthetic chemistry have developed a wide variety of chemical products and efficient chemical formulations to control the development of unwanted vegetation. Many types of chemical herbicides have been described in the literature, and a large number are commercially available.

Unwanted, many such herbicides have phytotoxicity both to the affected agricultural crop and to the weeds to be controlled. Thus, there is a permanent need for selective herbicides that control weeds that occur frequently but do not adversely affect crop plants when applied at herbicide-efficient doses.

In US patents 4780127, 4938796, 5006158 and 5089046, there are presented 2- (substituted benzoyl) -1,3-cyclohexandionic compounds, with the general structure:

© where X, Q and Z have the meanings set out below. These dionic compounds have been shown to be effective pre-emergent and post-emergent herbicides compared to a wide variety of herbs, broad-leaved weeds and weeds. U.S. Patent 56,68089 discloses one of these compounds, 2- (2'-nitro-4'-trifluoromethylbenzoyl) -1,3-cyclohexandione, as a selective herbicide for maize. In addition, PCT application WO 97/27748 shows metal chelates of 2- (substituted benzoyl) -1,3-cyclohexandionic compounds, which have been shown to be chemically stable for a long time under both conditions. of normal temperature, as well as in extreme temperature conditions.

The basic cyclohexandione has a very strong phytotoxic effect. In contrast, the metal chelates of 2- (substituted benzoyl) -1,3-cyclohexandionic compounds effectively combat a large number of weeds, without having any substantial phytotoxic effect on agricultural crops.

The disadvantages mentioned are eliminated by applying, according to the invention, the method of selective control of the undesirable vegetation of an agricultural crop, which includes the application of an effective amount of herbicide which is in the form of a metal chelate, of a 2 (substituted benzoyl) -1 , 3-cyclohexandione, selected from 2- (2'-nitro-4'-methylsulfonylbenzoyl) -1,3-cyclohexandione, 2- (2'-nitro-4'-methylsulfonylbenzoyl) -1,3-cyclohexandione and 2- (2 ' chloro-4'-methylsulphonylbenzoyl) -1,3-cyclohexanedione.

The invention relates to methods for the selective control of weeds and other unwanted vegetation from an affected agricultural crop, such as wheat. In one embodiment according to the present invention, the method comprises the post-emergent application of a herbicide-efficient amount of metal chelate of 2- (substituted benzoyl) -1,3-cyclohexandione

RO 121460 Β1 on the spot with such weeds and other types of vegetation. In another embodiment according to the invention, the method comprises the post-emergent application of a herbicide-efficient amount of metallic chelate of 2- (substituted benzoyl) -1,3-cyclohexandione on site 3 with such weeds and other vegetation. , the respective metal chelate being formulated as microcapsules. 5

The term herbicide is used to represent a compound that fights or modifies plant growth. The term herbicidal effective amount is used to indicate the amount of such compound that is required to produce a combating or modifying effect. Combat or modification effects include 9 all deviations from natural development, for example: destruction, retardation, leaf drying, albinism, dwarfism and others. The term plant refers to all the physical parts of an 11 plant, including seeds, seedlings, seedlings, roots, tubers, stems, luxuries, leaves and fruits. 13

The invention relates to the use of metallic chelates of the dionic compounds with herbicidal action for the selective control of weeds and other unwanted vegetation from a certain agricultural condition, such as wheat. These herbicidal ionic compounds generally have the formula I:

wherein X represents a halogen atom; a straight or branched chain alkyl or alkoxy group containing up to six carbon atoms, optionally substituted with one or more -OR ¹ groups or one or more halogen atoms; or a group selected from nitro, cyan, 27 -CO2 R ² , -S (O) m R ¹ , -OtCHȚȚOR ,, -COR ² , -OSO ₂ R ⁴ , -NR ² R ³ , -SO ² NR ² R ³ , -CONR ² R ³ and -CSNR ² R ³ ; 29

R ¹ represents a straight or branched chain alkyl group containing up to six carbon atoms, optionally substituted with one or more halogen atoms; 31

R ² and R ³ each independently represent a hydrogen atom or a straight or branched chain alkyl group containing up to six carbon atoms, optionally substituted 33 with one or more halogen atoms;

R ⁴ represents a straight or branched chain alkyl group, an alkenyl or alkynyl group having up to six carbon atoms, optionally substituted with one or more halogen atoms; or a cycloalkyl group containing from three to six carbon atoms; 37 each Z independently represents halogen, nitro, cyano, S (O) _m R ⁵ , OS (O) mR ⁵ , C 1 -C 6 alkyl, C 1 -C 6 alkoxy, C 1 -Cg haloalkyl, C 1 -Cg haloalkoxy, carboxy, C 1 -C 6 alkylcarbonyloxy, C 1 -C 6 alkoxy, C 1 -C 6 alkylcarbonyl, C 1 -C 6 alkylcarbonyl, amino, C 1 -C 6 alkylamino, C 1 -C dialkylamino, independently having a number of carbon atoms mentioned in each alkyl group, 41 C 1 -C 6 alkylcarbonylamino _{. 6} , C 1 -C 8 alkoxycarbonylamino, C 1 -C 6 alkylaminocarbonylamino, C 1 -C dialkylaminocarbonylamino, having an independent number of carbon atoms 43 mentioned in each group C 1 -C 6 alkyl, alkoxycarbonyloxy, C 1 -C 6 alkylaminocarbonyl, dialkylaminocarbon phenylcarbonyl, substituted phenylcarbonyl, phenylcarbonyloxy, substituted 45 phenylcarbonyloxy, phenylcarbonylamino, substituted phenylcarbonylamino, phenoxy or substituted phenoxy; 47

R ⁵ represents cyano, -COR ⁶ , -CO ² R ⁶ or -S (O) mR ⁷ ;

R ⁶ represents hydrogen or a straight or branched chain alkyl group containing 49 to six carbon atoms;

RO 121460 Β1

R ⁷ represents C 1 -C ⁶ alkyl, C 1 -C 8 haloalkyl, C 1 -C 8 cycloalkyl, C ₃ -C ₈ cycloalkyl, optionally substituted by halogen, cyan or C 1 -C 6 alkyl; or phenyl optionally substituted by up to 3 halogen nail identical or different nitro, cyano, C ^ haloalkyl, C ^ C. ,, C _r C ₄ alkoxy or -S (O) _m R ^0;

R ⁸ represents C3-C4 alkyl, halogen or cyano, -phenyl or benzyl substituted alkyl; each Q independently represents C 1-4 alkyl or -CO ² R ⁹ wherein R ⁹ is C 1 -C ₄ alkyl; m is 0.1 or 2;

n is 0 or an integer from 1 to 4;

r is 1, 2 or 3; and z is 0 or an integer from 1 to 6.

In the sense used herein, the terms halogen and halo include fluorine, chlorine, bromine and iodine atoms. In polyhalogenated groups, the halogens may be the same or different. The term substituted by the terms substituted phenylcarbonyl, "substituted phenylcarbonyloxy, substituted phenylcarbonylamino and substituted phenoxy" represents 1 to 5 substituents, which may be the same or different, selected from: halogen, nitro, cyan, S (O) _m R ² , alkyl C C 1 -C 6 alkoxy, C 1 -C 1 haloalkyl, C 1 -C 1 haloalkoxy, carboxy, C 1 -C 6 alkylcarbonyloxy, C 1 -C 6 alkylcarbonyl, C 1 -Cg alkoxycarbonyl, C 1 -C 6 alkylcarbonylamino, C 1 -C 4 alkylamino C 1 -Cg dialkylamino, having an independent number of carbon atoms mentioned in each group.

The 2- (substituted benzoyl) -1,3-cyclohexandionic compounds of formula I are described, inter alia, in US Pat. Nos. 47,801,749,4938,796,500,6158 and 50,890,46, the content of which is included by reference in the specification.

The herbicidal 2- (substituted benzoyl) -1,3-cyclohexandionic compounds, intended for use according to the invention, can be prepared by the processes described in the aforementioned patent publications or by applying and adapting the methods known or described in the literature.

The 2- (benzoyl substituted, 3-cyclohexandionic compounds used especially in the present invention include those wherein z is 0; X is chloro, bromo, nitro, cyano, C ₁ -C ₄ alkyl, -CF ₃ , -S (O ) _m R ¹ or -OR ¹ ; n is 1 or 2; and each Z is independently chlorine, bromine, nitro, cyano, C 1 -C 6 alkyl, -OR ¹ , -OS (O) mR ⁵ or -S (O) _m R ^5. Examples of preferred cyclohexandionic compounds are 2- (2'-nitro-4'-methylsulfonylbenzoyl) -1,3-cyclohexandione, 2- (2'-nitro-4'-methylsulfonyloxybenzoyl) -1,3-cyclohexandione and 2- (2'-chloro-4'-methylsulfonylbenzoyl) -1,3-cyclohexandione.

Compounds of formula I may exist in enol tautomeric forms, which may form geometric isomers. Furthermore, in certain cases, different substituents may generate optical isomers and / or stereoisomers. All of these forms are part of the compounds useful in the present invention.

Metal chelates of 2- (substituted benzoyl) -1,3-cyclohexandionic compounds of formula I are described, inter alia, in WO 97/27748, the content of which is included in the description. Metal chelates of compounds 2- (substituted benzoyl, 3-cyclohexandionic have the general structure:

EN 121460 Β1 where X, Q and Z have the meanings above and Me represents a slow di- or triva-1 metal ion, such as Cu * ² , Co ⁺² , Zn * ² , Ni * ² , Ca * ² , Al * ³ , Ti * ³ and Fe * ³ .

Herbicidal metal chelates of 2- (substituted benzoyl) 3 -1,3-cyclohexandionic compounds, used in the present invention, can be prepared by the processes described in the aforementioned PCT application or by applying and adapting the known or 5 methods described in the literature Specialized.

Metal ions that can be used to obtain metal chelated compounds according to the present invention include di- or trivalent metal ions, such as Cu * ² , Co * ² , Zn * ² , Ni * ² , Ca * ² , Al * ³ , Ti * ³ and Fe * ³ . The choice of a specific metal ion to form metal chelate depends on the 9 dionic compound to be chelated and the resistance of the metal chelate complex. Without being strictly related to the theory, it was found that the resistance of the metal chelated complex is directly related to the release rate of tricetone from the metal chelated complex, which in turn is related to the selectivity of the metal chelated compounds according to the invention. One of skill in the art can easily determine the appropriate metal ion to be used with a specific specific dionic compound, without further experimentation required. Preferred metal ions are 15 ions of divalent transition metals, in particular Cu * ² , Ni * ² , Zn * ² and Co * ² , especially being Cu * ² . 17

Any suitable salt, which could be a di- or trivalent metal ion source, can be used to form the metal chelate of the dionic compound according to the invention. Particularly suitable salts 19 include: chlorides, sulfates, nitrates, carbonates, phosphates and acetates.

It has also been found that the stability and activity of the metallic chelating herbicidal compositions 21 according to the present invention are pH dependent. The pH of metal chelating compositions should be between about 2 and about 10, preferably between about 23 3 and about 7. In general, it is considered that for Cu * ² chelating compositions, the pH should be either between about 4 and 6; for Co * ² between about 3 and 5; and for Ni * ² 25 and Zn * ² about 5. The optimum pH for a metal chelate composition can be determined using routine experimental techniques. 27

The metal chelate of 2- (substituted benzoyl) -1,3-cyclohexandionic herbicidal compounds can be formulated in the same way as herbicides are generally formulated. 29 The choice of formulation and how to apply it for a given herbicidal compound may influence its activity and the choice must be made accordingly. Herbicidal compositions may be formulated as granules dispersible in water, as wettable powders, as powders or powders, as suspensions or as controlled release forms, such as microcapsules. The metal chelate formulation of 33 2- (substituted benzoyl) -1,3-cyclohexandionic compounds with herbicidal action, intended for use in the present invention, can be prepared by the processes described in the aforementioned patent application 35 or by the application and adaptation of known methods. or described in the chemistry literature. The microencapsulation processes of the herbicidal composition have been described 37 in US 4285720 and 4956129 and US patent application 08/354409 and may also be prepared by applying and adapting the methods known or described in the literature. The object of the formulation, however, is to apply the composition to the place where the control is desired by a convenient method (that is, post-emergence application). The place represents the soil, as well as the 41 vegetation.

Formulations containing metallic chelates of herbicidal herbicidal compounds of formula I can be applied by conventional methods on the surfaces to be controlled. Formulations containing a herbicidal metal chelate according to the invention may be obtained in the form of premixtures with other herbicides or may be tank mixtures with one or more additional herbicides or other agricultural compositions. Specific examples of other herbicides that can be included in a herbicidal formulation with metal chelates of the invention include acetanilide, tralkoxide, bromxinil and its esters, tiafluamide, MCPA and its esters, 2,4-D and its esters 49, and fluroxipyr meptil.

In practice according to the present invention, the metal chelate of the 2- (substituted benzoyl) -1, 3-cyclohexandionic compounds with herbicidal action is applied post-emergently to the place where the undesirable vegetation is to be combated. The application doses depend on the plant species and the desired degree of control. In general, the application doses are between about 5 and about 500 g / ha.

The following are 3 non-limiting examples, which are illustrative only and are not representative for all the tests performed.

Example 1. All metal chelated compounds, used in the 1,3-cyclohexandione formulations of this example, were prepared using a mixing and grinding process, except Formulation C, which was obtained using a precipitation process. Both the mixing and grinding process and the precipitation process are described in detail in PCT application 97/27748, the description of which is included, by reference, in the description.

Twelve days after sowing the seeds in flat aluminum vessels (containing soil consisting of 2 parts sandy clay on 1 peat side), formulations were applied post-emergently in the form of 1,3-cyclohexandione suspension (at the doses in Table 1 of below) to the following plant species: Galium aparine (GALAP), Chenopodium album (CHEAL), Matricaria odorora (MATIN) and wheat.

The vessels were placed in the greenhouse and evaluated at 6 and 21 days after application (DAA ”). The injury was evaluated as a percentage control, the percentage control being the total injury of the plants, due to all the factors, including: the inhibited emergency, the piticism, malformations, albinism, chlorosis and other types of injuries. The control dose ranges from 0 to 100 percent, where 0% represents the lack of effect, the increase being equal to the untreated control and 100% represents complete destruction.

The obtained results (as an average of 3 determinations) are summarized in table 1.

co in Γ-

ΟΟ

RO 121460 Β1

CD CN

CN— CN

CN <0

S S —ξ cj CD O

Weed control activity,% MATIN 21 days 66 100 100 100 a 44 72 85 00 45 73 06 84 79 100 100 CHEAL 21 days 100 100 100 100 100 100 100 100 100 o o o o 100 100 100 100 o o GALAP 21 days 75 54 66 o o 64 75 83 86 83 87 84 66 93 94 68 66 Phytotoxicity in wheat,% 21 days a r 22 58 a a a a a a co a a a r 6 days 38 45 53 65 i a CN CN CN a CN a CN a a a co The dose applied g i.a./ha 12.5 25 50 100 9'2L 25 50 100 12.5 25 50 100 12.5 25 50 o o Molar ratio Dion / Metal 2/5 CN CN Formulation Control 1 (Unchelated) Formulation A (Cu Chelate) Formulation B (Cu Chelate) Formulation C (Cu Chelate)

ο Οί

Weed control activity,% MATIN 21 days 100 00 co 55 66 66 o o 100 100 100 100 93 100 65 66 100 100 CHEAL 21 days 100 100 100 100 100 100 100 100 o o r ~ o o T “ 100 100 o o 100 o o r— 100 GALAP 21 days 44 v CO 84 100 63 99 94 66 99 t— r- 66 ⁸⁶ 64 68 84 100 Phytotoxicity in wheat,% 21 days a 04 a 4 04 20 38 04 00 a- 00 CO a σ> 35 6 days 00 25 33 2. 3 33 38 43 20 28 35 40 28 35 40 45 The dose applied g i.a./ha 12.5 25 50 100 12.5 25 50 o o 12.5 25 50 100 12.5 25 50 o o Dion / Metal molar ratio 2/5 χ- 04 2/5 OJ Formulation Formulation D (Co Chelate) Formulation E (Co Chelat) Formulation E (Zn Chelate) Formulation G (Zn Chelate)

CO CM

CO LO

CO

or <0

CM

A

Weed control activity,% MATIN 21 days 100 100 100 100 100 I_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ o o CHEAL 21 days i 100 100 100 o o 100 100 GALAP 21 days 85 59 78 83 100 94 Phytotoxicity in wheat,% 21 days CO co co CD 25 48 6 days 20 30 30 40 45 I 53 The dose applied g.i.a./ha 12.5 25 12.5 25 50 100 Dion / Metal molar ratio 2/5 2/5 Formulation Formulation H (Ni Chelate) Formulation I (Ca Chelate)

RO 121460 Β1

From these results, it is evident that the phytotoxicity of 1,3-cyclohexandione formulations to wheat was reduced by chelation. Herbicidal activity of formulations of

1,3-cyclohexandione on weeds and other undesirable vegetation was, however, only slightly affected by chelation. In addition, it is also evident from these results that the activity of the 1,3-cyclohexandione formulation varied depending on the metal ion used to form the metal chelated compound.

Example 2. Chelated metal compounds, used in the suspension formulations a

The 1,3-cyclohexandione in this example were prepared using the mixing and grinding process as described in Example 1. Furthermore, a process essentially identical to that described in Example 1 was recommended for post-emergent application of suspended formulations of 1,3-cyclohexandione (at the doses shown in table 2 below) in flat aluminum vessels, containing the following plant species: CHEAL;

Amarantus retroflexus (AMARE), Polygonum convolvulus (POLCO), Brassica kaber (wild mustard) (SINAR), Thlaspi arventse (THLAR), Brassica canpestris (BRSNN), wheat (TRZAS); and barley (HORVS). The injury was assessed at 8 and 32 days after application (DAA).

The results obtained (as a mean of 4 determinations) are presented in table 2.

cm α>

CO IO a T " CO IO b- A) X ^- CO v- <N 04

RO 121460 Β1

Weed control activity% (32 days) THLAR 32 days 85 X σ> 66 100 100 100 06 94 66 100 100 100 SINAR 32 days 92 66 86 97 100 100 100 66 100 100 100 66 POLCO 32 days 53 £ 94 100 100 100 98 99 88 100 100 CHEAL 32 days 100 100 100 100 100 100 100 O o 100 100 100 100 BRSNN 32 days 69 86 89 97 100 100 06 82 89 89 95 100 AMARE 32 days 80 00 00 97 98 100 100 100 86 66 O o 100 100 Phytotoxicity in wheat and barley TRZAS, HORVS,% HORVS 32 days A a A a M · co X " - A - CO tut 8 days a NT co co - 00 A A a a - a TRZAS 32 days IO - CM IO T " 59 A a a a 34 64 8 days Μ * CD X ^- 24 34 44 A a a a Dosage g i.a./ha 3125 6.25 12.5 25 50 100 6.25 12.5 25 50 100 two hundred Formulation Control 2 (Unchelated) Formulation J (Cu Chelate)

RO 121460 Β1

These data indicate that the copper chelate of 2- (substituted benzoyl) -1,3-cyclohexandione, formulation J, shows a 16-fold increase in selectivity compared to wheat at the preliminary evaluation compared with the un-chelated formulation (Control 2). The activity of weed control of the formulation of copper chelate was approximately the same as that of the non-chelated formulation.

Example 3. The metal chelated compounds used in formulations of 1,3-cyclohexandione 7 in this example were prepared using the mixing and grinding process as described in Example 1. Control 3 and Formulation K were formulated as suspensions and Formula 9 L as microcapsules.

Using a process essentially identical to that described in Example 1, the 1,311 cyclohexandione formulations were applied post-emergently, at the doses presented in table 3 below, in flat aluminum vessels, containing the following plant species: AMARE, BRSNS, POLCO , 13 SINAR and TRZAS. The injury was assessed at 6 and 22 days after application.

The results obtained (as an average of 4 determinations) are presented in table 3.

co m h ~

CD

RO 121460 Β1

COiON-Oit ·> - T- 1- <- CM co in N- σ>> - co in

CM CM CM CM CO CO CO CO

co 3 Φ -Q .2 V. c a c <£ £ c E '5 cc, N -S a -c c 5 CC N • e of a c Weed control activity,% SINAR 22 days 87 85 97 o o T “ 100 1 1 1 97 92 93 95 96 1 1 1 POLCO 22 days 48 65 83 97 00 co 1 1 1 55 67 62 ¹ 89 92 1 1 t BRSNN 22 days 38 CO r CO co 00 96 1 1 and 65 56 65 73 90 1 1 1 AMARE 22 days 56 85 06 97 66 1 1 1 72 s 88 97 1 1 1 CC a c c • s c CC> < • ci c Λ C ος Τ ' ΙΟ 'C> <c £ '-S' c > c c ie '5 s' • C c CC CC s a JJ ^{1 1} J Phytotoxicity in wheat,% TRZAS (R) 22 days • 1 1 00 co V 25 59 80 1 1 t V But 33 69 6 days 1 1 1 26 40 50 58 <a 1 1 1 CD CD BUT r ~ - 49 TRZAS (K) 22 days 1 1 a CD 00 58 a 00 t 1 t CO N 00 33 74 6 days 1 1 1 1 2. 3 29 34 09 CD 1 1 A a CD 39 CO JZ N CO OQ CD 2.5 into the the x ~ 20 40 80 160 320 2.5 m a 20 40 80 160 320 CC c E c Formulation Control 3 (Unchelated) Formulation K (with chelate)

and

CQ

O Say

Weed control activity,% SINAR 22 days 88 78 88 66 98 1 1 1 O O - 1 O o. 22 days ²⁵ i 28 45 99 84 1 I 1 BRSNN 22 days 39 A V (D co • AMARE 22 days 20 26 45 75 95 • • Phytotoxicity in wheat,% TRZAS (R) 22 days | 1 1 t LO CD a 33 58 6 days 1 <A - a IO TRZAS (K) 22 days 1 1 - co co 38 99 6 days 1 1 1 - a T " a 39 Dosage g i.a./ha 2.5 LO a 20 40 80 160 320

<D i— ra

D

E

_i ω <i> L_

And u_

The LL

Ra3 ra

Φ .c o

Ό O <D

O <0 Q.

E

CD

LO

RO 121460 Β1

The above data indicate that the copper chelate of 2- (substituted benzoyl) 1-1,3-cyclohexandione (Formulation K) has improved selectivity over the unelated formulation (Control 3). These data also indicate that the selectivity of copper chelate 3 of 2- (substituted benzoyl, 3-cyclohexandione) was further enhanced by microencapsulation (Formulation L).

Claims (8)

1. A method of selective control of unwanted vegetation in an agricultural crop, which comprises applying, in the affected area, an effective amount of herbicide, which is in the form of a metal chelate, of a 2- (substituted benzoyl) -1 , 3-cyclohexandione selected from 2- (2'-11 nitro-4'-methylsulfonylbenzoyl) -1,3-cyclohexandione, 2- (2'-nitro-4'-methylsulfonyloxybenzoyl) -1,3cyclohexandione and 2- (2 ' chloro-4'-methylsulphonylbenzoyl) -1,3-ciclohexandionă.13 The method of claim 1, wherein the metal chelate of 2- (substituted benzoyl) -1,3-cyclohexandione contains a metal ion selected from the group consisting of copper, cobalt, zinc, nickel, 15 aluminum, calcium, titanium and iron. The method of claim 2, wherein the metal ion is copper.17 The method of claim 1, wherein the pH of the metal chelate of 2- (substituted benzoyl) -! , 3-cyclohexandione is in the range 2 ... 10.19 The method of claim 4, wherein the pH of the metal chelate of 2- (substituted benzoyl) -! , 3-cyclohexandione is in the range 3 ... 7.21 The method of claim 1, wherein the metal chelate of 2- (substituted benzoyl) -1,3- cyclohexandione is applied post-emergently.23 The method of claim 1, wherein the metal chelate of 2- (substituted benzoyl) -1,3- cyclohexandione is microencapsulated. 8. The method of claim 1, wherein the agricultural crop in which the undesirable vegetation is combated is wheat.27